Natural abundance 13C nuclear magnetic resonance methods have been previously used by this laboratory to study intracellular gelation of sickle hemoglobin. In the present project we have extended this work to characterize the proton-enhanced NMR spectrum of normal red cells. We found that normal erythrocytes display a reproducible spectrum attributable to physically immobilized membrane lipid and immobilized membrane-associated protein, presumably cytoskeleton. Binding of hemoglobin to membrane was not detected. This technique should be useful in further studies of erythrocyte physiology and the physiology of nucleated cells.